Opaque sheet material



- without ill effect.

Patented May 9, 1944 UNITED STATE OPAQUE SHEET MATERIAL William R. Collings and land, Mich., assignors "Jompany, Midland, Mich, a corporation of --lichigan Toivo A. Kauppi, Midto The Dow Chemical No Drawing. Application June 12, 1940,

- Serial No. 340,148

(Cl. 106-493) I 7 Claims.

This invention relates to an improvedopaque sheet material, suited primarily for making playing cards but also useful for making book covers, surfaces for slide rules, and the like.

The ordinary paper or cloth playing cards suffer from the defects that they become limp and dirty after a comparatively short period of use. Further, they cannot be cleaned without becoming'and remaining limp. Cards made of a cellulose acetate material have been recently introduced on the market which overcome these defects. They retain their snap or crispness over long periods of use and may be washed in water However, there are certain dlmculties in the manufacture of cellulose acetate'playing cards which prevent cellulose acetate from being generally accepted as the ideal constructional material for such items. The main difficulty is one concerning printing of the opaque sheet.

Owing to the smoothness and non-porosity of cellulose. acetate sheets as ordinarily manufactured, coupled with the small compatibility of cellulose acetate with many of the ingredients of printing inks as commonly made, permanent,

' wear-resistant prints cannot be made on them.

In order to secure adhesion of, printing inks to of improved printability with common letter press or drying oil inks or with solvent-type inks.

A further object is the provision of a crisp opaque sheet material from which rinted play ing cards can be easily made.

Another object is to provide washableplaying cards having a long life and to which printing adheres throughout their life.

' These and related objects are attained by making sheet material from a composition comprising 65 to 85 parts by weight of organo-soluble ethyl cellulose of not to exceed 46.5 per cent ethoxy content, and preferably one of ethoxy content between 44.5 and 16.5 per cent, inclusive,

- and a pigment in opacity producing quantity, ordinarily from 10 to 30 parts by weight. The

the cellulose acetate sheet, it is necessary to first render its surface slightly rough or matte either by surface saponification or mechanically, i. e. using an embossing or abrading technique. A

second requirement for satisfactory printing on.

cellulose acetate sheets is the use of special inks comprising high-boiling solvents which are capable of penetrating into or of being absorbed by the sheets. Solvents which do this and yet have sufiiciently lowvolatility to be usable in printing inks on the common, unenclosed kinds of printing presses are few in number, and all of them penetrate cellulose acetate sheets rather slowly, i. e. they lack bite. Inks made from them are slow in drying out after application to the sheets and consequently the printing process is complicated.

It has been proposed to make playing cardsand other articles from pigmented sheets of ethyl cellulose, methyl cellulose and benzyl cellulose. Of these, methyl cellulose is not organo-soluble and is unsuited to the suggested use, benzyl cellulose is too soft, and the ethyl cellulose which has been commercially available, i. e.

one of 4'? to 49 per cent ethoxy content, is too soft and does not have the required snap.

It is, accordingly, an object of the present invention to provide an opaque sheet material composition may contain, in addition, from 1 to 10 parts by weight of a plasticizer for ethyl cellulose, of the type having a yield point hardness greater than 100. Yield point hardness is defined as the ratio (expressed as a percentage) of the hardness of an ethyl cellulose film containing 15 percent of its Weight of a plasticizer to the hardness of an unmodified ethyl cellulose film, hardness being in turn defined in terms of the yield'point of the film, as in equation 2. given by' Bass and Kauppi', Ind. Eng. Chem. 29, p. 680, 1937.

Ethyl cellulose of the aforesaid ethoxy type is the only available cellulose ether whichyields sheets having the requisite snap for making playing cards. Playing cards comprising ethyl cellulose of ethoxy content between 44.5 and 46.5 per cent, inclusive, have a constant crisp handle; throughout their long life, comparable with that of good quality paper cards after considerable use. Paper cards are originally too hard and stiff, and then, after use, they become satisfactorily flexible at about the time they become too worn for further service. The new ethyl cellulosecards take and retain ink, when printed, and are washable and long lived. Of other cellulose ethers, some form sheets which are too limp for use as playing cards; others are incapable of being dissolved to form a homogeneous solution in organic solvents from which sheets can be made conveniently, and yet others are solvents, and in sheet form is dimensionally less stable than the preferred product. The recited ethoxy range of from 44.5 to 46.5 per cent is thus seen to be quite critical for the production of practical articles of the type here discussed.

The maximum amount of pigment usable in applicants new sheets is limited as aforementioned because it has been found that if much larger quantities than that specified the compositions become too brittle for the intended use. Therefore, to maintain uniform density and opacity of the finished sheet, it is necessary to use not more than about 30 parts by weight of pigment per 65 to 85 parts by weight of ethyl cellulose. A lower' limit of parts of pigment by weight is imposed because if smaller quantities than this are used the new sheets are insufficiently opaque for their intended uses. Absolute opacity of the sheet is a necessity in the case of playing cards in order to prevent the possibility of the indicia on the face of a card. being recognized when viewing the back of the card, especially when the card is being held between the eye of the observer and a bright light. For this reason, it is preferred, when making sheet stock for playing cards, to use more than and less than 30 parts of white pigment for each 65 to 85 parts by weight of ethyl cellulose. The kind of pigment used is not material to the present invention, and it may be white or oil-shades, as, for example, cream, pale blue, grey, etc. For making playing cards, we prefer to use either "Titanox or a mixture of Titanox" and zinc sulphide. Titanox is titanium dioxide pigment. Either alone or in admixture with zinc sulphide or other suitable white pigment it contributes a bright whiteness and opacity to sheets containing it, when employed in the recited proportions. Pigmented articles of colors other than white or the off-shades of white may of course be produced within the scope of the annexed claims defining the present inventio A minor quantity of a hardening plasticizer may be added as aforesaid to the composition from which the sheets are made. Such an addition is not essential when makingplaying cards, but is helpful when employing high pigment concentrations, and, when making opaquedrawn, or other heat-formed articles, the addition of plasticizer is desirable. Suitable plasticizers include tri (p-tertiarybutylphenyl) phosphate, di (ptertiarybutylphenyl) mono 5 tertiarybutyl 2- xenyl) phosphate, polycyclohexyl diphenyloxides, polybromodiphenyloxides, and chlorinated polyphenyls containing more than 60 per cent of chlorine such as those products sold under the names: .Aroclor 1262, Aroclor 2565, and Aroclor 4465.

The sheets of the present invention may be conveniently made by casting upon a support a solution of ethyl cellulose in the critical range of 44.5 to 46.5 per cent ethoxy content, having the requisite amount of pigment in suspension there- .in, and thereafter evaporating the solvent. Any

of the methods known to the film casting art,-

whichare adapted to give thick films, may be employed. In order that ethyl cellulose playing cards may handle in a similar manner to the paper cards to which card players have become accustomed, sheets intended for'the manufacture of cards should have a thickness of about 0.25

to about 0.35 millimeter, i. e. from about 0.010 to about 0.015 inch.

The new sheets are printable by either common drying oil-base inks or by solvent-W96 i ks.

The latter are. preferred as they may be used in a manner more economical of drying time after printing. No pretreatment of the ethyl cellulose sheets is necessary when using either type of ink. Both types yield adherent, wear-resistant prints. Either the lithographic or letter-press methods of printing, or any of the many variations of these methods, may be used.

Further, to simulate paper cards in surface properties such as slipperiness and light dill'using action, it is desirable. to coat the cards with a light diffusing lacquer. Suitable lacquers for this purpose may be made bydissolving ethyl cellulose of 48.5 per cent or higher ethoxy content in mixtures of aliphatic and aromatic hydrocarbons containing less than 20 per cent by volume of the latter, so as not to soften the base sheet, and dispersing camauba wax therein. A thin uniform coating of the lacquer may be spread over the printed card to deposit a coating of dry thickness of the order of less than 0.0005 inch.

As illustrative of the invention. the following example showing a method of making a sheet suited to the manufacture of playing cards is given. v j Pigment chips were made by milling parts by weight of ethyl cellulose of 45 per cent ethoxy content ,and 40 parts by weight of Titanox A on a hot two-roll mill. After grinding, the chips were added to 400 parts by weight of a 15 per cent solution of ethyl cellulose of similar type and agitated until dispersed. The resulting solution, carrying about 25 parts of "Tltanox A" in uniform dispersion for each 75 parts of ethyl cellulose, was cast to yield a film of thickness (when dry) of 0.28 millimeter (about 0.011 inch). The filmsheet printed well when using both drying oil base and solvent-type inks. Cards cut from it possessed sn ap" were completely opaque and had satisfactory "handle" and feel."

By way of contrast, when similarly pigmented sheets were madefrom ethyl cellulose of about 47.5 per cent ethoxy content, the sheets lacked snap, and were too soft and too easily abraded for use in the manner and for the purposes to which the herein-described lower ethoxy. material is suited.

Other modes of applying our invention may be employed instead of the one explained, change being made as regards the materials employed, provided the ingredients stated by any of the following claims or the equivalent of such stated ingredients be employed.

We therefore particularly point out and distinctly claim as our invention:

1. Opaque sheet material, printable with both drying oil inks and solvent-type inks, containing as the predominant ingredients ethyl cellulose of from 44.5 to 46.5 per cent ethoxy content, and, for each 65 to 85 parts by weight thereof, from 10 to 30 parts by weight of an opacity producing pigment and from 1 to 10 parts of an ethyl cellugose plasticizer of hardness index greater than 10 cellulose plasticizer of hardness index greater than 100.

-3 Opaque sheet material, printable with both 2. Opaque sheet material, printable with both drying oil inks and solvent-type inks, containing drying ,oil inks and solvent-type inks, containing as the predominant ingredients ethyl cellulose of from 44.5 to 46.5 per cent ethoxy content, and, for each 65 to 85' parts by weight thereof, from 10 to 30 parts by weight of an opacity producing white pigment comprising titanium dioxide and from 1 to 10 parts of an ethyl cellulose plasticizer of hardenss index greater than 100.

4. Opaque sheet material of thickness between 5. Opaque sheet material of thickness between about 0.25 and 0.35 millimeter, printable with both drying oil inks and. solvent-type inks, consisting essentially of ethyl cellulose 01 from'44.5 to 46.5 per cent ethoxy content, and, for each 65 to 85 parts by weight thereof, from 1 to 10 parts of an ethyl cellulose plasticizer of hardness index greater than 100, and from 10 to 30 parts of an opacity producing white pigment comprisabout 0.25 and 0.35 millimeter, printable with 10 ing titanium dioxide.

both drying oil inks and solvent-type inks; consisting essentially of ethyl cellulose of from 44.5 to 46.5 per cent ethoxy content, and, for each 65 to 85 parts by weight thereof, from 10 to 30 parts of an opacity producing white pigment comprising titanium dioxide and from 1 to 10 parts of methyl cellulose plastizer of hardness index greater than 109.

6. A playing card comprising the opaque sheet material claimed in claim 4.

7. A playing card comprising the opaque sheet material claimed in claim 5.

WHJJAM R. COLIINGS. TOIVO A. KAUPPI. 

